Electric fans for patio umbrellas are known but are typically fairly complex, difficult to assemble, and AC powered.
For example, in U.S. Pat. No. 5,007,811 an electric motor turns a rotatable drive ring supported on the umbrella shaft by a number of bearings through a fairly complex gear train. In U.S. Pat. No. 5,765,582 an electric AC motor is connected by a belt to a pulley which in turn drives a gear in the base of the umbrella stand.
Other patents in this field include Nos. 5,172,711; 5,273,062; 5,349,975; 5,887,771; 5,967,161; 3,177,881; 1,148,332; and Des. 409,369, all incorporated herein by this reference. None of these fans are suitable for use by children nor are they particularly adapted for a child's play set which includes an umbrella, a play table, and a number of chairs.